Process for hot extruding metals

ABSTRACT

The process of hot extruding metals and alloys which are subject to surface contamination at their deformation temperature is improved by coating the billet surface, while cold, with a thin layer of a powdered metal such as copper, and thereafter placing a second coating of a powdered amorphous material on top of the metal powder layer. The amorphous material is capable of forming a continuous protective layer when heated to the temperature at which surface contamination takes place during the extrusion operation.

United States Patent de Charsonville PROCESS FOR HOT EXTRUDING METALS Inventor: Jacques de Charsonville,

- Llsle-Adam, France Assignee: Cefilac, Paris, France Filed: Mar. 14, 1973 Appl. No.: 341,232

References Cited UNITED STATES PATENTS 3,580,019 5/1971 Beresnev et a1. 72/47 Primary Examiner-C. W. Lanham Assistant ExaminerE. M. Combs Attorney, Agent, or FirmWebb, Burden, Robinson & Webb 5 7 ABSTRACT The process of hot extruding metals and alloys which are subject to surface contamination at their deformation temperature is improved by coating the billet surface, while cold, with a thin layer of a powdered metal such as copper, and thereafter placing a second coating of a powdered amorphous material on top of the metal powder layer. The amorphous material is capable of forming a continuous protective layer when heated to the temperature at which surface contamination takes place during the extrusion operation.

4 Claims, No Drawings PROCESS FOR HOT EXTRUDING METALS BACKGROUND OF THE INVENTION Field of Invention My invention relates to the hot extrusion of metals and alloys and, more particularly, to the hot extrusion of metals and alloys which are particularly subject to surface contamination by contact with external agents such as the atmosphere, extruding lubricants or metal tooling. Examples of such metals whose deformation temperatures make them particularly subject to surface contamination are titanium, zirconium and their alloys.

DESCRIPTION OF THE PRIOR ART The surfaces of extruded products made from metals and alloys which are subject to surface contamination can be severely damaged by external agents such as the vitreous lubricant which is directly applied to the billet in accordance with the teachings of US. Pat. No. 2,538,917 and the like.

Presently there are at least three practices which can be employed to treat the billetprior to deformation. The billet can be clad by a metal sheath, for example, copper or steel, so that the entire surface of the billet is covered, including that of the bore, if the billet has been previously bored. This method gives sound products. but it is slow and expensive. The surface of the billet may be metallized by gun spraying copper on it. Or,

I the outer surfaces of the billet may be metal clad while the billet bore is treated by gun spraying previously described. The latter two methods are fast and economical but they do not always insure satisfactory protection of the billet so that the extruded products may still show defective surface conditions caused by the surface contamination when hot.

SUMMARY OF THE INVENTION My invention avoids the drawbacks of the prior art by insuring that a tight protective coating is applied to the billet over its entire surface so that when it is hot extruded, there is no surface contamination. The invention consists in applying-on the exposed surfaces of the billet, while cold. a first thin layer of metal powder and thereafter a second layer of an amorphous powdered material having sufficient wettability to provide a continuous tight protective layer when heated to the temperatures at which extrusion takes place and at which the metal is susceptible to surface contamination.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first layer can be applied by gun spraying onto all exposed surfaces ofthe billet while the billet is cold. This first layer, which is a metal powder such as copper, is preferably applied so that the extruded product will be clad with a layer of this metal ranging in thickness between 0.05 and 0.1 mm. Under these conditions, the cross-sectional dimensions of the as extruded product are very close to those of the product obtained by removing its coating. The second layer of material, which is an amorphous powder. can be applied onto the cold billet having the thin metal layer in any known manner. For example, the billet may be dipped into a suspension ofa vitreous material in a liquid capable of evaporating during heating, or by spraying the suspension onto the metal layer, or by spreading it with a brush, etc.

The amorphous powder can perform another function if properly selected. A material can be selected which has a viscosity at the extrusion temperature appropriate for lubricating the extrusion operation, as taught in particular by French Pat. No. 966,773. A vitreous material comprised of salts, oxides or their mixtures is particularly adaptable to the dual purpose.

After the billet has been treated with the two layers, it is heated in the normal manner. During heating, the volatile liquid evaporates and the grains of amorphous or vitreous material adhere to the copper layer, then they become welded to one another and thus build up the desired continuous layer. The total protection insured by the two layers operates until the extruded product has completely cooled.

My process has been employed on a titatium alloy having the following composition by weight: carbon 0.08%, nitrogen 0.06%, hydrogen 0.01 25%, oxygen 0.30%, iron 0.25% and balance titanium. The titanium alloy was extruded into tubes having an outside diameter of mm and a wall thickness of 7 mm. The starting billet was cylindrical and previously cold bored. The billet was 400 mm in length, 143 mm in outside diameter and 64 mm in inside diameter. The outside front edge of the billet had been rounded into a 20 mm radius. The billets were descaled by shot blasting prior to receiving their coating in accordance with my invention. The billets were coated by gun spraying on their inside and outside lateral surfaces, as well as their end faces with a 0.5 mm copper powder layer. The billet was then coated on all exposed surfaces by water spraying with a layer of enamel having a viscosity of about 1000 poises at 620C. The billet was heated to 720C prior to the hot extrusion.

The billet was extruded in an extrusion press having available 1500 metric tons of force and equipped with a container having a 148 mm diameter and a die with a circular opening 70.8 mm in diameter. A cylindrical extrusion mandrel 55.4 mm in diameter was employed. The lateral surfaces of the mandrel and the container were coated with a thin layer of molybdenum disulfide and the entry face of the die was protected by a disc of agglomerated enamel powder in accordance with known practice. After the hot billet was inserted into the container and extruded, it was cooled to room temperature. The copper was removed from both the inside and outside surfaces of the extruded tube and a careful inspection indicated that the surfaces were free of any defect or any trace of surface contamination.

I claim:

I. In a process including heating and hot extruding billets of metals and alloys subject to surface contamination at their deformation temperature, the improvement comprising:

A. coating the billet surface, while cold, with a thin layer of powdered metal;

B. coating the coated surface of the billet, while cold,

with a powdered amorphous material; and

C. forming a continuous protective layer on the billet surface by heating the coated billet to the temperature of hot cxtrusion, said layer protecting against surface contamination of the billets.

2. The improvement of claim I wherein the powdered amorphous material is further characterized by having a viscosity appropriate for lubricating the billet surface during extrusion.

3. The improvement of claim I wherein the powdered metal is copper.

4. The improvement of claim 1 wherein the powdered metal layer is applied to a thickness between 0.0l and 0.5 mm.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. I 3, 890,818

DATED 1 June 24, 1975 INVENTORQQ i Jacques de Charsonville It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown betow:

After the line listing the application serial number insert --Foreign Application Priority Data Mar. 16, 1972 France 72/09. l33-.

En'gncd and Stealed this sixteenth Day Of September 1975 [SEAL] A ttest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner nfPalents and Trademarks 

1. IN A PROCESS INCLUDING HEATING AND HOT EXTRUDING BILLETS OF METALS AND ALLOYS SUBJECT TO SURFACE CONTAMINATION AT THEIR DEFORMATION TEMPERATURE, THE IMPROVEMENT COMPRISING: A. COATING THE BILLET SRUFACE, WHILE COLD, WITH A THIN LAYEER OF POWDERED METAL; B. COATING THE COATED SURFACE OF THE BILLET, WHILE COLD, WITH A POWDERED AMORPHOUS MATERIAL; AND C. FORMING A CONTINUOUS PROTECTIVE LAYER ON THE BILLET SURFACE BY HEATING THE COATED BILLET TO THEE TEMPERATURE OF HOT EXTRUSION, SAID LAYER PROTECTING AGAINST SURFACE CONTAMINATION OF THE BILLETS.
 2. The improvement of claim 1 wherein the powdered amorphous material is further characterized by having a viscosity appropriate for lubricating the billet surface during extrusion.
 3. The improvement of claim 1 wherein the powdered metal is copper.
 4. The improvement of claim 1 wherein the powdered metal layer is applied to a thickness between 0.01 and 0.5 mm. 